(-)-Mycousnine is a microbial metabolite and derivative of usnic acid originally isolated fromM. nawaethat has antibacterial and antifungal activities.^1,2It is active against the Gram-positive bacteriaB. subtilis,K. rhizophila, andS. aureus(MICs = 4, 8, and 4 g/ml, respectively) but not the Gram-negative bacteriaE. coli,S. typhimurium, andK. pneumoniae(MICs = >128 g/ml for all).²(-)-Mycousnine is also active against the fungiT. mentagrophytes,T. rubrum, andC. albicans(MICs = 25, 25, and 100 µg/ml, respectively).¹

1.Sassa, T., and Igarashi, M.Structures of (-)-mycousnine, (+)-isomycousnine and (+)-oxymycousnine, new usnic acid derivatives from phytopathogenic Mycosphaerella nawaeAgric. BioI. Chem.54(9)2231-2237(1990) 2.Lee, J., Lee, J., Kim, G.J., et al.Mycousfurans A and B, antibacterial usnic acid congeners from the fungus Mycosphaerella sp., isolated from a marine sedimentMar. Drugs17(7)422(2019)